Application regarding continuous-flow tubular reactors in chemical synthesis is a novel reaction technique, which has been developed in the past years. This technology is also being applied in the agro-food processing. A tubular reaction system comprises the following units: mixers, heat exchangers, pumps, reactors, controllers and the like; its pipeline size encompass tens of millimeters to hundreds of microns, thus various reagents during flowing can be quickly and uniformly mixed, thereby demonstrating the outstanding mass transfer and heat transfer performance. Moreover, processing conditions can be conveniently optimized, the increase of production capability also can be achieved, the period required for product output, from research to production, is shortened. On the other hand, it has been reported that various physical fields, such as electric field, sound field, magnetic field, electromagnetic field combined with the tubular reactor was applied for chemical reaction and agro-food processing, causing the change in the mass transfer and reaction kinetic owing to the reaction medium having a specific dielectric properties and magnetic conductive capacity.
Existing electric field technologies containing ohmic heating and pulsed electric field have been widely applied in the food and agriculture. Technical characteristics is that raw materials are located between discharge areas in a channel or chamber, and the sample as a dielectric material is influenced by an alternating electric field at different field intensity and frequency, thereby causing cell electroporation or the change of mass transfer. However, these technologies utilize charged electrodes or electrode plates for the processing, which result in ion polarization, electrochemical reaction, and metal contamination. Therefore, the application of these electrotechnologies is limited, especially in acid and alkaline mediums.
The physical field, such as the magnetic field, sound field, electric field, and electromagnetic field, can be acted as a control parameter of the reaction system. Application of these fields will facilitate or inhibit some chemical reactions. However, the generator of these fields is bulky, sophisticated, and costly. Also, they are not flexibly arranged or installed in a compact system. Thus, applications of these generators as field control units in an array reaction system are limited, which make multi-dimensional reaction condition operation in matrix form impossible.
For instance, the generator of the magnetic field is permanent magnet or Helmholtz coil; the generator of the electromagnetic field is a magnetron equipped with an oscillation generator. The magnetic field and the electromagnetic field acting on inorganic and organic substances can avoid the generator is contact with the reaction medium directly. If the generators of the magnetic field and the electromagnetic field are arranged in an array configuration, the volume of the system may be bulky, and thus the equipment is costly. Moreover, the magnetic field and the electromagnetic field act on the flowing reaction medium in a limited area; the field effect on other location (away from the discharge region) may dissipate. On the other hand, charged electrodes and power supplies as generators of electric fields, makes the electrodes inserted into the reaction medium. Thus, electrode surface corrosion, metal leakage, electrochemical reaction, and sample contamination are inevitable during long-term treatment or vigorous reaction. And, more charged electrodes inserted into the reaction medium in an array configuration may cause serious contamination.
In conclusion, the existing reaction technique cannot effectively utilize the electric fields as control parameter in a matrix form for chemical reaction and agro-food processing.